1. Field of the invention
The present invention generally relates to an electric generation control apparatus for a vehicle alternator, capable of controlling output of the vehicle alternator based on an electric generation control signal transferred from an external control device such as an electronic control unit (ECU), and capable of detecting and diagnosing electric generation state of a vehicle alternator and of transferring the diagnosis result to the ECU.
2. Description of the Related Art
There are well-known various types of electric generation control apparatus for electric generators such as vehicle alternators. One of them is capable of keeping a generation voltage at a constant voltage (for example, 14.5 Volts) that is higher than a battery open voltage (for example, 12.8 Volts) in order to perform a rapid battery charging, and capable of changing a control voltage according to the driving condition of a vehicle based on power generation control parameters transferred from the external control device such as an electronic control unit (ECU) mounted on the vehicle.
For example, the following two patent documents (1) and (2) have been known, that have-disclosed LIN (Local Interconnect Network) protocol as one of serial data communication protocols.
(1) U.S. Pat. No. 5,767,636 (corresponding to the Japanese patent publication No. JP 3,505,882, pages 5 to 12, and FIGS. 1 to 31); and
(2) U.S. Pat. No. 5,629,606 (corresponding to the Japanese patent publication No. JP 3,531,771, pages 5 to 11, and FIGS. 1 to 10).
However, the technique disclosed by the patent document (1) involves a following drawback. Because a vehicle alternator is directly mounted on a vehicle, when the ignition for a vehicle engine generates noises, the ignition noises are always on a communication bus and overlapped to control signals transferred between the power generation control apparatus and the ECU through the communication bus. In General, the ignition noises are changed according to vehicle condition and vehicle engine condition because an optimum ignition voltage is changed according to the magnitude of engine load. Accordingly, such an ignition noise causes signal-wave fluctuation and thereby causes checksum error or parity error. The occurrence of such an error obstructs the normal communication between the power generation control apparatus and the ECU, and reduces the capability to monitor the power generation state of the vehicle alternator by the external control apparatus and to control the power generation by the vehicle alternator.